Roof construction has a long and diverse architectural history. From the standpoint of construction alone, roofs for homes, buildings, stadiums or arenas or other constructs must not only provide a cover for the building but must be able to resist immense roof loads such as high winds and rain and, in many areas, snow and ice.
A typical roof type is that which is incorporated into a wood-framed dwelling. When the width of the roof area is less than about 30 feet, the roof surface--composition shingles or tile or slate placed on sheathing or plywood--may be supported on rafters or roof trusses which run from the peak of the roof to its eaves. When the width of the area to be covered exceeds about 30 feet, wooden roof trusses are usually used instead of rafters, and additional support may be furnished by the use of longitudinal members, known as purlins, that span the trusses. Industrial buildings often use essentially this same construction, except that the trusses, purlins and roofing are generally fabricated from steel or prestressed concrete or other high load-bearing materials.
No matter what type of roof construction is used, roof design must always accommodate the need for adequate attic ventilation. Satisfactory attic ventilation is necessary for many reasons. Attic ventilation not only removes heat and moisture from attic spaces in hot weather, but removes attic condensation in cold weather to prolong building structure and roof material life and to preserve the viability of the attic insulation.
Traditionally, in order to afford adequate ventilation, rafters or roof trusses were customarily extended well beyond the exterior wall of the dwelling or building, to form vented eaves. Ordinarily, the soffit, or horizontal underside of the eave, was fitted with vents of varying designs, which vents allowed air to pass into the attic from the outside. Hot, moist air inside the attic could then exit through roof vents, known in the art, positioned higher than the vents in the eave and thus able to create a chimney effect in the attic.
One typical vent for an eave of a roof is exemplified in U.S. Pat. No. 4,702,149 to Speer, in which tubes are provided to allow air to enter through the soffit. The tubes are constructed so that condensed moisture from inside the roof is collected and drained from a drain trap beneath the ventilating tubes. The general concept exemplified by Speer is the use of the soffit as an area of attic ventilation.
Simple vents in soffit are well known, and may comprise strip vents, spot vents or other ventilation apertures provided in the soffit. Usually the ventilation apertures are covered with either a louvre or screening material to discourage infestation of insects and other small life forms. U.S. Pat. No. 2,991,709 to Haddix represents a simple soffit vent of this type. U.S. Pat. No. 4,315,455 to Shaklee discloses a more elaborate variation on this theme, in which a central air flow space through the soffit is provided with a foraminous covering and an adjacent air scoop panel which may be positioned in either an open or in a closed position.
Other patents which allow attic ventilation from the area of the eave with ventilation channels of various types include U.S. Pat. No. 255,608 to Eaton, U.S. Pat. No. 3,972,164 to Grange, U.S. Pat. No. 4,200,034 to Listle et al., U.S. Pat. No. 4,222,315 to Weirich and U.S. Pat. No. 4,807,409 to Sells.
None of the prior art under-roof apertures for attic ventilation address the problem which the present invention solves, however. The traditional extension of roof rafters or roof trusses out over the exterior wall, to form eaves, was adopted in the first place to create what was believed to be soffit area necessary for attic ventilation. Requirements were developed over the years for amounts of ventilation which were required to be included in soffit structures, and a certain minimum soffit area itself became a typical minimum building standard, usually a 12-16 inch overhang. Creating large surface areas of soffit for the purpose of creating screened or louvred apertures in such a construct accounted for considerable construction cost. To make matters worse, not only did the existence of the eave create additional expense in the soffit design and construction, but increased roof area and need for roofing materials and labor commensurate with the roof area of the eave meant that the roofs themselves were bigger and more expensive than they would have needed to be merely to cover the building. A need remained in the roof construction industry, therefore, for a soffit vent in which eave construction could be simplified, roof area minimized and attic ventilation enhanced.